Bearings
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Mopar Fanatic
Joined: May 2011
Posts: 346
Likes: 8
From: Boring, Oregon
Bearings
Alright, I need experienced people to reply only. I dont want any opinions with out reasoning.
I'm going to be rebuilding a LA 360 motor in a 70 challenger soon and I want to know the best performance bearing on the market and WHY.
Right now the motor has edelbrock aluminum heads, intake and 600cfm carb, roller rockers, big bump stick and stock bottom end.
Plan is to put KB pistons in it to up the cr a bit and get some more hp. I want to work over the heads a little also.
So I'm wanting to know what the best performance bearings are on the market today. Also, if you know what rings i should use. (Cast or moly)
Any other tips/tricks would be helpful to help make some more power too. I'm not a novice, so don't talk to me like i am.
Thanks!
I'm going to be rebuilding a LA 360 motor in a 70 challenger soon and I want to know the best performance bearing on the market and WHY.
Right now the motor has edelbrock aluminum heads, intake and 600cfm carb, roller rockers, big bump stick and stock bottom end.
Plan is to put KB pistons in it to up the cr a bit and get some more hp. I want to work over the heads a little also.
So I'm wanting to know what the best performance bearings are on the market today. Also, if you know what rings i should use. (Cast or moly)
Any other tips/tricks would be helpful to help make some more power too. I'm not a novice, so don't talk to me like i am.
Thanks!
Mopar Fanatic
Joined: Sep 2009
Posts: 486
Likes: 29
From: Amarillo, Tx
Well Its actually dependant on how the engine will be used... In a street motor with limited strip use I would use the 1/2 groove... There are all sorts of pro's con's on this matter... ( google it and check the many forums it drags up and then check a few out) Some camps say its NOT a good idea as it reduces bearing surface, others swear by them... Its more up to you as to what makes YOU more comfortable... To me its a toss-up... If i had a set I would use them, if not use the 1/2. M2C... ( and i have been told NOT to express my opinions before)
Mopar Fanatic
Joined: Sep 2009
Posts: 486
Likes: 29
From: Amarillo, Tx
AND here is why I say its all just an opinion... (a copy and paste from one of the many forums the subject brings up)
That's not true at all, you've got it backwards. You may be confusing this with the fact that it is harder on the rod at TDC, which is due to the rod being in tension. And tension is bad due to its affects on fatique life of the metal, where compression is actually a good thing. A couple of examples of compression goodness are forgings and shot peening, both of which leave you with desireable compressive stresses (and forgings also leave you with desireable metal grain structure). And this is good for fatique life of the metal.
Back to the bearing issue, at TDC exhaust, the only load is from the piston/rod assembly being forced to change direction. But at BDC you still have the force needed for said assy to change direction the other way, PLUS the downward combustion force. From the standpoint of mass being forced to reverse direction, it is a wash whether you talk about TDC or BDC, but when you add the combustion force, it isn't even a close comparison. For example, my 540 combustion pressure is around 1,200 psi, and when spread out over the piston, it equals about 19,080 lbs of downward force. So in this case, you have around 20,000 lbs MORE force on the BOTTOM bearing shell, just from one piston.
That is precisely why bottom bearing shells don't/shouldn't use a groove. Having no groove gives it more square inches of bearing to support the load. This is why it is a bad idea to use full groove main bearings, you'd be REDUCING the load carrying capacity of the bearing. The top shell isn't any where near as critical, so the groove there is not detrimental. In fact, the best way to go, is to use 3/4 groove main bearings. They give improved oiling with no loss of load carrying capaicity, because the extra parts of the groove are on the sides where it isn't supporting any load anyway. 540 RAT Expert
Posts: 559Joined: Thu Feb 08, 2007 7:21 pmLocation: Southern California
That's not true at all, you've got it backwards. You may be confusing this with the fact that it is harder on the rod at TDC, which is due to the rod being in tension. And tension is bad due to its affects on fatique life of the metal, where compression is actually a good thing. A couple of examples of compression goodness are forgings and shot peening, both of which leave you with desireable compressive stresses (and forgings also leave you with desireable metal grain structure). And this is good for fatique life of the metal.
Back to the bearing issue, at TDC exhaust, the only load is from the piston/rod assembly being forced to change direction. But at BDC you still have the force needed for said assy to change direction the other way, PLUS the downward combustion force. From the standpoint of mass being forced to reverse direction, it is a wash whether you talk about TDC or BDC, but when you add the combustion force, it isn't even a close comparison. For example, my 540 combustion pressure is around 1,200 psi, and when spread out over the piston, it equals about 19,080 lbs of downward force. So in this case, you have around 20,000 lbs MORE force on the BOTTOM bearing shell, just from one piston.
That is precisely why bottom bearing shells don't/shouldn't use a groove. Having no groove gives it more square inches of bearing to support the load. This is why it is a bad idea to use full groove main bearings, you'd be REDUCING the load carrying capacity of the bearing. The top shell isn't any where near as critical, so the groove there is not detrimental. In fact, the best way to go, is to use 3/4 groove main bearings. They give improved oiling with no loss of load carrying capaicity, because the extra parts of the groove are on the sides where it isn't supporting any load anyway. 540 RAT Expert
Posts: 559Joined: Thu Feb 08, 2007 7:21 pmLocation: Southern California
Thread Starter
Mopar Fanatic
Joined: May 2011
Posts: 346
Likes: 8
From: Boring, Oregon
Well Its actually dependant on how the engine will be used... In a street motor with limited strip use I would use the 1/2 groove... There are all sorts of pro's con's on this matter... ( google it and check the many forums it drags up and then check a few out) Some camps say its NOT a good idea as it reduces bearing surface, others swear by them... Its more up to you as to what makes YOU more comfortable... To me its a toss-up... If i had a set I would use them, if not use the 1/2. M2C... ( and i have been told NOT to express my opinions before)
AND here is why I say its all just an opinion... (a copy and paste from one of the many forums the subject brings up)
That's not true at all, you've got it backwards. You may be confusing this with the fact that it is harder on the rod at TDC, which is due to the rod being in tension. And tension is bad due to its affects on fatique life of the metal, where compression is actually a good thing. A couple of examples of compression goodness are forgings and shot peening, both of which leave you with desireable compressive stresses (and forgings also leave you with desireable metal grain structure). And this is good for fatique life of the metal.
Back to the bearing issue, at TDC exhaust, the only load is from the piston/rod assembly being forced to change direction. But at BDC you still have the force needed for said assy to change direction the other way, PLUS the downward combustion force. From the standpoint of mass being forced to reverse direction, it is a wash whether you talk about TDC or BDC, but when you add the combustion force, it isn't even a close comparison. For example, my 540 combustion pressure is around 1,200 psi, and when spread out over the piston, it equals about 19,080 lbs of downward force. So in this case, you have around 20,000 lbs MORE force on the BOTTOM bearing shell, just from one piston.
That is precisely why bottom bearing shells don't/shouldn't use a groove. Having no groove gives it more square inches of bearing to support the load. This is why it is a bad idea to use full groove main bearings, you'd be REDUCING the load carrying capacity of the bearing. The top shell isn't any where near as critical, so the groove there is not detrimental. In fact, the best way to go, is to use 3/4 groove main bearings. They give improved oiling with no loss of load carrying capaicity, because the extra parts of the groove are on the sides where it isn't supporting any load anyway. 540 RAT Expert
Posts: 559Joined: Thu Feb 08, 2007 7:21 pmLocation: Southern California
That's not true at all, you've got it backwards. You may be confusing this with the fact that it is harder on the rod at TDC, which is due to the rod being in tension. And tension is bad due to its affects on fatique life of the metal, where compression is actually a good thing. A couple of examples of compression goodness are forgings and shot peening, both of which leave you with desireable compressive stresses (and forgings also leave you with desireable metal grain structure). And this is good for fatique life of the metal.
Back to the bearing issue, at TDC exhaust, the only load is from the piston/rod assembly being forced to change direction. But at BDC you still have the force needed for said assy to change direction the other way, PLUS the downward combustion force. From the standpoint of mass being forced to reverse direction, it is a wash whether you talk about TDC or BDC, but when you add the combustion force, it isn't even a close comparison. For example, my 540 combustion pressure is around 1,200 psi, and when spread out over the piston, it equals about 19,080 lbs of downward force. So in this case, you have around 20,000 lbs MORE force on the BOTTOM bearing shell, just from one piston.
That is precisely why bottom bearing shells don't/shouldn't use a groove. Having no groove gives it more square inches of bearing to support the load. This is why it is a bad idea to use full groove main bearings, you'd be REDUCING the load carrying capacity of the bearing. The top shell isn't any where near as critical, so the groove there is not detrimental. In fact, the best way to go, is to use 3/4 groove main bearings. They give improved oiling with no loss of load carrying capaicity, because the extra parts of the groove are on the sides where it isn't supporting any load anyway. 540 RAT Expert
Posts: 559Joined: Thu Feb 08, 2007 7:21 pmLocation: Southern CaliforniaThanks for a thorough reply. This motor will pretty much only see street uses with very little strip. I see why the guy suggests 3/4 groove bearings for rods.
If anyone else has suggestions with reasoning on other build tips/tricks or why i should use moly rings vs cast please chime in.
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